1. Field of the Invention
The present invention relates to a cleaning device for cleaning an image bearing member and to an image forming apparatus having the cleaning device, such as a copying machine, a laser printer, a facsimile device or the like.
2. Description of Related Art
An image forming apparatus such as a copying machine, a laser printer, a facsimile device or the like is generally arranged to form an electrostatic latent image on the surface of a photosensitive drum (an image bearing member), to develop (visualize) the electrostatic latent image into a toner image by applying toner to the electrostatic latent image, to transfer the toner image to a transfer member such as paper or the like, and to fix the image transferred by heating. With the image forming apparatus arranged in this manner, after the transfer of the toner image, the photosensitive drum has some remnant toner remaining untransferred on the surface thereof and also some powdery remnants of paper such as fiber or some components of paper sticking thereto. These sticking matters are removed and recovered from the photosensitive drum by means of a cleaning device.
A cleaning device which is popular among other known cleaning devices is arranged to scrape such sticking matters off the surface of the photosensitive drum, i.e., the image bearing member, by causing a cleaning blade (cleaning member) to abut on the image bearing member.
The known cleaning device is sometimes provided with an auxiliary member for making it capable of more stably carrying on its cleaning function. The auxiliary member is, for example, a magnetic toner brush (toner supply means). The magnetic toner brush is arranged, on the lower stream side of the cleaning blade in the rotating direction of the photosensitive drum, to resupply the cleaning blade with the toner scraped off by the cleaning blade from the surface of the photosensitive drum. With the scraped-off toner re-supplied in this manner, a predetermined amount of toner can always be supplied to a nip between the surface of the photosensitive drum and the cleaning blade to ensure a stable friction coefficient between the two members at the nip, so that the cleaning function can be stably carried out.
The arrangement of the above-stated image forming apparatus having the magnetic toner brush is, however, ineffective in undoing a fused sticking of the toner to the surface of the photosensitive drum in cases where the toner tends to stick to the surface of the photosensitive drum (including electrostatic sticking). The cause of this problem is considered to be as follows. In a case where toner sticks to the surface of a photosensitive drum due to the uneven surface condition of the photosensitive drum or the like, the amount of toner supplied to the fused sticking part by the magnetic toner brush becomes larger than the amount of toner removed at the nip between the photosensitive drum surface and the cleaning blade. As a result, the fused sticking of toner increases. It is known that this phenomenon tends to take place under a high-temperature and high-humidity ambient conditions. Further, since the toner is sticking to the photosensitive drum, the condition of the surface of the photosensitive drum also has a great influence on this phenomenon. Therefore, the fused sticking of toner is apt to take place particularly in a case where a photosensitive drum having a long durability is used under a high-temperature and high-humidity ambient condition.
The present invention has been made in view of the above circumstances, and an object of the invention is to provide a cleaning device capable of preventing a fused sticking of toner to an image bearing member (a photosensitive drum), and an image forming apparatus using the cleaning device.
To attain the above object, in accordance with an aspect of the invention, there is provided a cleaning device for removing residual toner from a surface of an electrophotographic photosensitive member after a transfer process, the cleaning device comprising a cleaning blade composed of an elastic member for scraping residual toner off the surface of the photosensitive member by abutting on the surface of the photosensitive member, and toner supply means, disposed in an upper stream side of the cleaning blade as viewed in a moving direction of the surface of the photosensitive member, for supplying toner to a nip between the surface of the photosensitive member and the cleaning blade by causing toner to stick to the surface of the photosensitive member, the toner supply means including switching means for switching the toner supply means between a first mode of causing toner to stick to the surface of the photosensitive member to supply toner to the nip between the surface of the photosensitive member and the cleaning blade and a second mode of not causing toner to stick to the surface of the photosensitive member, or of decreasing an amount of toner to be stuck to the surface of the photosensitive member, the second mode being selectable when a main switch of an image forming apparatus having the cleaning device mounted therein has become turned on.
Further, according to another aspect of the invention, there is provided an image forming apparatus using the above cleaning device.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.